1. Field of the Invention
The present invention relates to a composition for forming an electron emission source, a method for preparing an electron emission source, and an electron emission source prepared therefrom. In particular, the present invention relates to a composition for forming an electron emission source that has decreased carbon deposits after heat treatment, a method of preparing such an electron emission source, and an electron emission source that has a very small amount of the carbon deposits. The present invention also relates to an electron emission device that includes the electron emission source.
2. Description of the Related Art
An electron emission device is a display apparatus that applies a voltage between an anode and a cathode to form an electric field, which causes electrons to be emitted from an electron emission source of the cathode. The device then bombards electrons into a fluorescent material at the anode to emit light.
A carbon-based material such as a carbon nanotube (CNT) is a promising electron emission source for an electron emission device because it has excellent conductivity and electric field focusing effect. In addition, the driving voltage of the carbon nanotubes is low due to its low work function and excellent field emission properties, and thus, it can be applied in large area. An electron emission source employing a carbon-based material is described in U.S. Pat. No. 6,436,221, for example.
An electron emission source comprising a carbon-based material, such as a carbon nanotube, can be prepared by a deposition method or a paste method. These methods use a composition for forming an electron emission source comprising carbon nanotube powder.
In the paste method, the concentration of the carbon deposits that are present after heat treatment of the composition is excessively high compared to the concentration of the carbon-based material that comprises the resulting electron emission source. Thus, the carbon deposits may cover the carbon-based material or interfere with the vertical orientation of the carbon-based material. For this reason, a satisfactory field emission device with a long lifespan may not be obtained.